JPH10164758A - Individual operation detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an individual operation detector of simple structure which can conduct exact and instantaneous detection. SOLUTION: In a power system where a generator 36 for private power generation is connected on the downstream side of a power system whose power plant or substation is on the upstream side, a transformer 51 which superimposes a signal having higher frequency than commercial frequency and a receiver 52 which receives the signal are connected so that the transformer 51 may be positioned on upstream side and the receiver may be positioned on downstream side. If a signal from the transformer 51 is not obtained by the receiver 52, the system is shut down, which is discriminated as the individual operation of the generator 36. It is thus possible to keep the generator 36 parallel off from the power system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an islanding operation detecting device for detecting an islanding operation of a private generator connected to an electric power system, and more particularly to an islanding operation detecting device which has a simple structure and can be detected accurately and instantaneously. It is about.

[0002]

2. Description of the Related Art Along with recent deregulation policies, it has been accepted in the electric power field that a general company's factory or the like supplies surplus power for private power generation to a power system of a power company. In the future, it is expected that many companies will connect private power generation systems to power company power systems.

[0003] In such a private power generation facility, it is required to install an islanding operation detection device. The islanding operation detection device detects that, when the power system is shut off upstream due to an accident or the like, the islanding operation is an islanding operation in which power is supplied only from a private generator downstream, and such an islanding operation is performed. The generator must be disconnected from the grid immediately.

According to the distributed power system interconnection technical guideline (published by the Japan Electrical Association), the isolated operation detection method is a passive method (a voltage phase jump detection method, a third harmonic voltage distortion sudden increase detection method, There are a frequency change rate detection method) and an active method (frequency shift method, active power fluctuation method, reactive power fluctuation method, and load fluctuation method). One or more of the passive method and the active method can be combined. Has been requested.

[0005] Here, the passive system is a system that utilizes the fact that the balance between the supplied power and the load is lost and the voltage phase and the frequency are suddenly changed when the operation shifts to the isolated operation. The sudden change of the voltage phase due to the unbalance between the power generation output and the load is detected. In the third harmonic voltage distortion sudden increase detection method, when the current control type inverse converter is used, the sudden increase of the third harmonic dependent on the transformer is detected. In the detection and frequency change rate detection method, a sudden change in frequency due to imbalance between the power generation output and the load is detected.

[0006] In the active system, voltage and frequency fluctuations are applied to the generator, and the fluctuations are suppressed by the power from the power system at all times. In the frequency shift method, a frequency bias is given, and a frequency change due to this is detected.
In the active power fluctuation method, the active power is varied,
Voltage fluctuation, current fluctuation or frequency fluctuation is detected. In the reactive power fluctuation method, fluctuation is given to reactive power, frequency fluctuation or current fluctuation is detected, and in the load fluctuation method, parallel impedance is instantaneously inserted. Are repeatedly observed to detect a change in the magnitude of the fluctuation.

[0007]

In the passive method, changes in voltage phase and frequency also occur due to load fluctuations, so whether the detected change is due to normal load fluctuations or transition to islanding operation. There is a dead zone region for determining the state of the vehicle, and if the change to the single operation happens to be small, the single operation may not be detected.

[0008] The active system is excellent in that there is no dead zone, but it must synchronize fluctuations given to other private power generation facilities connected to the same system.

[0009] Further, in either system, it is necessary to detect the fluctuation by observing the voltage waveform of the electric power system or the generator, and to correctly determine that the fluctuation is caused by the shift to the islanding operation. , Accuracy is required for detection.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide an islanding operation detecting device which has a simple structure and which can accurately and instantaneously detect.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a power system in which a generator for private power generation is connected downstream of a power system having a power plant or a substation as an upstream. Also, a transmitter that superimposes a signal having a high frequency and a receiver that receives this signal are connected such that the transmitter is located on the upstream side and the receiver is located on the downstream side. Is not obtained, it is determined that the system has been disconnected and the generator has been operated independently, and the generator is disconnected from the power system.

[0012] A bypass device for bypassing the signal may be connected in parallel to a transformer inserted in a power system between the transmitter and the receiver.

[0013] One or more circuit breakers may be inserted in series upstream of the generator, and the generator may be disconnected from the power system by operating one of the circuit breakers.

[0014]

An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

As shown in FIG. 1, the individual loads 2 and 2 and the factory 3
A group of three units is connected. Although not shown, a power station or a higher-order substation is provided further upstream of the substation 1. In the substation 1, a transformer 11 and a circuit breaker 12 that cuts off a power system downstream of the transformer 11 are provided. A circuit breaker 21 is also inserted into each load 2 with respect to the power system. In each factory 3, a plurality of factory loads 32 are respectively connected downstream of the main circuit breaker 31 via circuit breakers 33, and the private power generation equipment 34 is also connected to the circuit breaker 31 downstream of the main circuit breaker 31. 35
Connected through. The private power generation facility 34 includes a generator 36 and a transformer 37.

In the islanding detection device of the present invention, a transmitter 51 for superposing and transmitting a signal having a frequency higher than the commercial frequency is connected between a transformer 11 and a circuit breaker 12 in a substation 1; On the other hand, a receiver 52 for receiving a signal from a transmitter 51 in the substation 1 is connected to the upstream side immediately adjacent to the transformer 37 in each factory 3, and the signal is obtained by the receiver 52. An operation circuit 53 for operating the circuit breaker 35 when not operated is provided.

The operation will be described below.

In the substation 1, the transmitter 51 superimposes a signal of a frequency of 1 kHz to 5 kHz on the power system and transmits the signal with a size that does not affect the power system.

On the other hand, in each factory 3, the receiver 5
2 takes out the signal from the power system and receives it.

When the power system of the power company is operating normally, the factory 3 of a general company receives power supply through the main circuit breaker 31. At the same time, the generator 36 for private use is also operated, and if there is surplus power, it can be supplied to the power system. As described above, in a state where the private power generation facility 34 has not shifted to the isolated operation, the private power generation facility 34
Continuity up to that point. Therefore, the receiver 52 can reliably receive the signal superimposed on the power system by the transmitter 51. Therefore, the operation circuit 53 does not operate, and the generator 36 is not disconnected from the power system.

When an accident or the like occurs in the power system, the substation 1
Then, the power system is cut off by the circuit breaker 12. For this reason, the private power generation facility 34 shifts to the isolated operation. When the private power generation equipment 34 shifts to the stand-alone operation, the power system is cut off by the circuit breaker 12, so that the signal superimposed on the power system by the transmitter 51 is also cut off. Therefore, the receiver 52 cannot receive the signal. Therefore,
It is determined that the operation is the islanding operation, and the operation circuit 53 operates the circuit breaker 35 to disconnect the generator 36 from the power system.

The circuit breaker operated by the operation circuit 53 is the circuit breaker 35 for shutting off only the private power generation facility 34. However, any circuit breaker located upstream of the generator 36 may be used. If the load capacity in the plant is smaller than the power generation capacity of the generator 36, the breaker 35 is not operated and the main circuit breaker 31 is operated, so that this factory 3
In this case, even if the power system is interrupted upstream due to an accident or the like, the private power generation equipment 34 is still connected, so that power can be supplied to each load 32, and the operation by private power generation can be continued.

According to the present invention, since it is determined that the upstream and the downstream are shut off based on the presence or absence of the signal, the isolated operation can be detected reliably and in a short time. Further, since it is not necessary to observe a voltage waveform or the like, it is not necessary to give active fluctuations, and it is not necessary to synchronize the fluctuations, the configuration of the apparatus becomes very simple. Further, the present invention can be easily applied to a case where a plurality of private power generation facilities are connected to the same system.

In some cases, a transformer is inserted in the power system. If a transformer is inserted in the power system between the transmitter 51 and the receiver 52, the superimposed signal from the transmitter 51 cannot always pass through the transformer, so that the input side and the output side of the transformer It is preferable to provide a bypass unit that bypasses the superimposed signal from the transmitter 51 between the two. A filter, a capacitor, or the like can be used as the bypass unit.

[0025]

The present invention exhibits the following excellent effects.

(1) Since it is determined that the upstream and downstream are cut off based on the presence or absence of a signal, the isolated operation can be detected reliably and in a short time.

(2) It is not necessary to observe a voltage waveform or the like.
Since there is no need to provide active fluctuations or to synchronize the fluctuations, the device configuration becomes very simple.

[Brief description of the drawings]

FIG. 1 is a power system diagram showing one embodiment of the present invention.

[Explanation of symbols]

 1 Substation 2, 32 Load 3 Factory 11, 37 Transformer 12, 21, 31, 35 Circuit breaker 34 Private power generator 36 Generator 51 Transmitter 52 Receiver 53 Operation circuit

Claims (3)

[Claims] A transmitter for superimposing a signal having a frequency higher than the commercial frequency on the power system in which a generator for private power generation is connected downstream of a power system having a power plant or a substation upstream. The receiver is connected to the transmitter so that the receiver is located on the upstream side and the receiver is located on the downstream side. When a signal from the transmitter cannot be obtained for this receiver, the system is disconnected and the generator is disconnected. And detecting that the generator is disconnected from the power system upon determining that the isolated operation has been performed. 2. The apparatus according to claim 1, wherein a bypass device for bypassing the signal is connected in parallel to a transformer inserted in a power system between the transmitter and the receiver. Islanding detection device. 3. The method according to claim 1, wherein one or more circuit breakers are inserted in series upstream of the generator, and one of the circuit breakers is operated to disconnect the generator from the power system. The islanding detection device according to claim 1 or 2.